1. Field of the Invention
The present invention relates generally to methods and apparatus for introducing medical instruments into the uterus. In particular, the present invention relates to a transcervical uterine access device which provides thermally insulated access to the uterus through the cervix and which substantially inhibits thermally conductive media from exiting the uterus around the access device and into the vagina.
"Minimally invasive" surgical procedures have recently been developed as alternatives to conventional "open" surgery. Of particular interest to the present invention, are minimally invasive surgical procedures relating to treatment of the uterus. More particularly, of interest to the present invention are least invasive and other surgical techniques which rely on a catheter to deliver heat to the interior of the uterus. As described in detail in U.S. Pat. No. 5,045,056 and co-pending application Ser. No. 08/266,037 (attorney docket no. 13178-8-2), the disclosures of which are incorporated herein by reference, the inner lining of the uterus, known as the endometrium, can be thermally destroyed by heating the endometrium to a temperature sufficient to effectuate necrosis. To heat the endometrium, a thermally conductive medium can be introduced into the uterus and maintained at a temperature sufficient to induce necrosis. The medium can be delivered to the uterus by a catheter which is inserted through the cervix and which is provided with a heating element to heat the medium within the uterus.
Such thermal treatment procedures can be problematic in certain respects. For instance, a cannula or sheath is typically inserted through the vagina and the cervix to provide an access channel or lumen into the uterus. It is difficult to provide a seal between the cervix and the cannula to prevent the medium from leaking around the cannula and outwardly toward the vagina. Leakage of hot medium past the cannula presents the possible risk of injury to the vagina and cervix.
A further problem can arise when heat from the catheter or the heated fluid is transferred through the cannula and to the vagina or the cervix. This heat transfer also presents the possible risk of injury to the vagina and cervix.
Another problem can arise when inserting the catheter through the cannula. The cannula may not be sufficiently anchored to the cervical os permitting the cannula to move within the cervix. Such movement is undesirable since it increases the potential for leakage.
For these and other reasons, it would be desirable to provide improved methods and apparatus for the introduction of a thermally conductive medium into the uterus to provide thermal treatment to the uterus. It would be particularly desirable to provide a transcervical uterine access device that could both provide access to the uterus for a catheter delivering the medium and substantially inhibit undesired release of the medium from the uterus.
2. Description of the Background Art.
Hysteroscopes providing visual access and working channels through the endocervical canal into the uterus are described in U.S. Pat. Nos. 4,911,148; 4,836,189; 4,779,612; 4,641,634; and 4,503,843. A cannula for introducing heated fluids and having an insulative sheath which engages the outer cervix is described in U.S. Pat. No. 5,242,390. An inflatable bladder for distending and heating the uterus is described in U.S. Pat. No. 4,949,718. A hysterography device having a cup at a distal end for seating on the cervix is described in U.S. Pat. No. 5,259,836.